TJ, the swapmeister, in this swap grassonfly, collects everyone's flies & sends them back to everyone involved so that you get an assortment of the patterns each tier has provided. The tiers also provide return shipping costs, a self addressed label for the return address & often return packaging.
I like to send flies in a stout box, such as a Priority Mail box, with the labeled return box inside & an Altoids can or similar box for the flies. If they get lost in the mail, I'm out the flies & the can, but not any great expense. Padded envelopes work well too for some swaps, but I prefer boxes as I've seen flies get crushed in envelopes or worse, the envelop gets torn open & the flies get lost.
The idea of swaps is to swap flies tied by the participants which lets folks see what types of flies others with similar interests like to tie & use. It's also a good way for those tiers with less experience to improve their skills, because once you get the flies back, you have an example of some very good flies to use as models.